Ideally the theory that one should select is the one which is the most frequently mentioned while conducting the literature review. However, there are times when one wants to adopt a completely different approach, in that case the said theory can be mentioned and than explain that you will take the concept further in light of the other theory because the older one has been used too often.

The most relevant theory should be applied, you can choose more than one but then you will have to have two main focuses in the study.

The existence of a number of theories means the existence of many possible explanations. One should not forget that evidence, and repeated evidence is consistent with many explanations. Therefore, careful research design is advised.

Part of it depends on the ROLE of the theory in your study.  If the theory framework will be the source of your data collection plan, then you need a theory that aligns most closely with your study research questions, participants, etc.  On the other hand, if you are looking for a theoretical framework for analysis in the Discussion section of your paper, then you could use more than one.  In fact, multiple ways of analysis in your discussion could be a good thing because the analysis would therefore be more rich.